Truth endures, falsehood collapses

וידו אוחזת בעקב עשו.

"And his hand was grasping the heel of Eisav" (Bereishis 25:26).

Yaakov was born holding Eisav's heel, and the Sefas Emes will draw a lesson from this image of grasping the very "end" of Eisav.

ז"ש שקר אין לו רגלים.

This is the meaning of "falsehood has no legs (sheker ein lo raglayim)."

The saying teaches that falsehood cannot stand — it has no firm footing and ultimately collapses.

כמ"ש במדרש עשו הא שוא שבראתי בעולמי כי כל שקר שאין אומרים אמת מתחלתו אינו מתקיים.

As it says in the Midrash: "Eisav — he is the falsehood (shav) that I created in My world," for any falsehood that does not state truth at its beginning does not endure.

Eisav represents pure falsehood. A lie that has no kernel of truth at its outset cannot last; only something with a true starting point can persist.

לכן ע"כ עשו יש בו משהו בראשו כמ"ש ראשית גוים עמלק.

Therefore, perforce, Eisav has some bit (of truth) at his head/beginning, as it says, "the first of nations is Amalek" (Bamidbar 24:20).

Even Eisav must have some small element of substance at his "head" (his beginning), which is why his descendant Amalek is called "the first of nations" — a deceptive prominence at the start.

אבל אחריתו עדי אובד.

"But his end is to perish" (Bamidbar 24:20).

Whatever apparent strength Eisav/Amalek has at the start, his end is utter destruction — falsehood has no lasting "legs."

ושפת אמת תכון לעד זהו שם יעקב.

"But the lip of truth shall be established forever" (Mishlei 12:19) — this is the name of Yaakov.

Yaakov embodies truth, which (unlike falsehood) endures forever — "established for eternity."

שמתקן עד העקב והסוף.

For he rectifies even unto the "heel" and the end.

Yaakov's grasp on Eisav's heel signifies that the power of truth reaches all the way to the very "end" — rectifying even the lowest, final point, which is where falsehood collapses.

וקושטא קאי:

"And truth stands (kushta kai)" (based on Shabbos 104a).

The Aramaic maxim "truth endures" seals the point: only truth has the staying power to remain standing to the very end, while falsehood ultimately falls.

Summary: Yaakov, born grasping Eisav's heel, embodies the principle that "falsehood has no legs" while "truth stands forever." Eisav is the personification of falsehood, which can only endure if it contains some kernel of truth at its beginning — hence Amalek is "the first of nations," with a deceptive substance at his head, yet "his end is to perish." Yaakov, by contrast, is "the lip of truth established forever," whose power reaches all the way down to the "heel" and the end. Falsehood collapses at its end; truth alone stands to the very last.